Question about extension box on Rodenstock 90mm HR-SW

[wding109]

Does any body know if the extension box on the 90mm HR-SW can be replaced with additional Rotaslide spacer/focus calibration tube/or sth similar?
Every time I try to mount this lens I need to take off the DB and put the extension box on, which is not quite convenient for me. So I am just wondering if there is a solution....

Thank you!

[jsiva]

Does any body know if the extension box on the 90mm HR-SW can be replaced with additional Rotaslide spacer/focus calibration tube/or sth similar?
Every time I try to mount this lens I need to take off the DB and put the extension box on, which is not quite convenient for me. So I am just wondering if there is a solution....

Thank you!

Theoretically possible, and I can test it for you if you like.  Three things to consider....1.  You'd need 3-4 rings to offset the back spacer; Hope you have a CMOS back, as LV focus will be the way to go, I doubt the fit will be exact enough for the arca charts to work; Distance from lens to sensor will be about the same, but distance to the "throat" of the camera will now be different.  Not sure how this may impact vignetting etc., during movements.

If you are really interested, and don't have the equipment, I can test it for you.

[wding109]

That will be great! thank you so much!
I don't have the CMOS back and not enough spacers for the testing...

[jsiva]

That will be great! thank you so much!
I don't have the CMOS back and not enough spacers for the testing...

Ok, give me the weekend.

[Wayne Fox]

I doubt the fit will be exact enough for the arca charts to work;

The charts are accurate only after figuring out an offset based on each lens and body anyway.  That offset may be a lot more than it would be using the standard spacer, but once the offset is calculated it can be applied to any of the focus settings.

All of the lenses of my arca setup are off by 3 to 5  numbers from the chart.  I made a little spreadsheet where I just plug in all the card numbers and the offset, and all the new numbers are calculated.  Printed it out to a PDF and now it's handy on my phone.

I wonder if adding all the rings to extend the lens forward would add enough weight/pressure so the tilt wouldn't hold.  Also seems it might be fine until the lens is shifted.

[Paul2660]

I would agree, the 90 HR-SW has enough mass that if you extended it out further to off set the back spacer you run the risk of too much front weight and the tilt gear may slip. Especially if add a hood or filters or both.

Back spacers are just part of the deal with the tech glass in medium telephoto and out.
90mm HR no spacer
90mm HR-W blue band. spacer
90mm HR-SW yellow band spacer

The 90 HR which I have is close to pushing the front weight with the number of front rings.
Don't forget 105mm HR. much lighter and no spacer. But of course not not the same glass as the 90 HR-SW

You might also reach out to Rod Klukas the U.S. Arca rep. Rod has tremendous product knowledge on all aspects of the Arca system.

Paul C

[Rod.Klukas]

Does any body know if the extension box on the 90mm HR-SW can be replaced with additional Rotaslide spacer/focus calibration tube/or sth similar?
Every time I try to mount this lens I need to take off the DB and put the extension box on, which is not quite convenient for me. So I am just wondering if there is a solution....

Thank you!

Paul, was correct about the weight. The 90mm is so heavy in its front group, that we decided a more balanced mounting by including the rear extension made the displacement far better.
Inconvenient at times but much more stable.
The HR 90mm W, the previous generation did not use glass of the density that the latest iteration does, and so was a bit lighter.  But the new one does and so the front glass group is very massive.
In fact, as with the 32mm from Rodenstock as well,
It is not recommended to ever carry your tripod/head/camera lens, over your shoulder like a shovel, as the mass may damage the shutter and de-center the front group causing uneven sharpness across the image plane.
Hope this helps,
Rod